The pilot was conducting a cross country flight in company with a Thruster ultralight. Near their destination he lost sight of this aircraft. After several minutes of searching, he located the Thruster on the ground. However, during several low passes he could not see the pilot. Fearing for the pilot's safety he elected to land. Just as the Skydart was about to touch down the pilot saw some rocks ahead on the intended landing area. He applied full power for a go around but the left maingear leg hit a rock and was torn off. The pilot closed the throttle and landed adjacent to the other aircraft, which had also suffered landing gear damage during a forced landing. The other pilot was uninjured but had left the scene minutes earlier seeking assistance.